PortalSiteMapProvider - sharepoint

Question

Everytime I instantiate a PortalSiteMapProvider instance it always defaults to the Root Web Site Collection.
I want to be able to acquire a site map from a different collection from an application page.
Because of this, the context defaults to the root web since this application page resides under _layouts and is not hosted under any site collection.
How do I acquire an instance to a site collection other than the root web from an application page?
Thanks.

Answer 1

You can't read another site collection's hierarchy through a PortalSiteMapProvider. E.g., if you are in Site Collection A, PSMP will only traverse A's tree, not B. You have to be in B to traverse B.
A workaround I implemented was to write a simple web service that runs in a site collection and takes a path as a parameter. It reads its own PSMP and writes an XML tree from that point in the hierarchy. Calling the web service living in SC-B from code running in SC-A is extremely fast, especially since the PSMP can rip through B's structure so quickly.
Edit:
Here are instructions for creating a web service in WSS3/MOSS.
Here is some totally non-functional code to get you headed in the right direction:
//method exposed through the web service
public XmlDocument GetTree(string path)
{
PortalSiteMapProvider psmp = PortalSiteMapProvider.GlobalNavSiteMapProvider;
SiteMapNode node = psmp.FindSiteMapNode(path);
return BuildXmlFromNode(node);
}
private XmlNode BuildXmlFromNode(SiteMapNode node)
{
XmlDocument xml = new XmlDocument();
reutrn BuildXmlFromNode(node, xml);
}
//recurses down the sitemapnode children
private XmlNode BuildXmlFromNode(SiteMapNode node, XmlNode xml)
{
XmlElement element = doc.CreateElement("Node")
element.SetAttribute("title", node.Title);
element.SetAttribute("url", node.Url);
xml.AppendChild(element);
foreach(SiteMapNode childNode in node.ChildNodes)
{
BuildXmlFromNode(childNode, element);
}
return xml;
}
Please note if you don't set a limit on the number of recursions and your site map hierarchy is very deep and/or wide, this could produce a HUGE xml document. Use with caution!